The present invention relates to a novel industrial process for producing high purity, low particle hydrochloric acid for use in semiconductor production.
The hydrogen chloride gas produced by chlorine electrolysis and subsequent burning of chlorine and hydrogen customarily contains impurities which is [sic] very difficult if not impossible to remove from the gas itself. Such impurities include for example arsenic, bromine and volatile organic impurities. Such impurities are difficult to remove even by passing the hydrogen chloride gas into water and subsequently subjecting the resulting hydrochloric acid to an adiabatic distillation.
It is known to produce hydrochloric acid in more or less high purity according to the following different methods:
1. Distillation of 20% hydrochloric acid
2. Distillation of a hydrochloric acid having a hydrogen chloride content of  greater than 20% and subsequent absorption of the released hydrogen chloride in the 20% hydrochloric acid distillate
3. Introducing hydrogen chloride gas from compressed gas bottles or a pressurized pipework system conveying hydrogen chloride into a receiver partly filled with water and provided with a cooling means
4. Subboiling distillation
These methods (1-4), however, do not permit production of a hydrochloric acid in the requisite purity (methods 1, 2, 3) or requisite concentration (methods 1 and 4).
A method suitable for producing small amounts of high purity hydrochloric acid has hitherto been carried out as follows: 37% hydrochloric acid is heated to expel hydrogen chloride gas. The hydrogen chloride gas is passed through a small retention column to remove droplets and subsequently into a receiver filled with ultrapure water. However, this method is only suitable for producing small quantities of hydrochloric acid, i.e. 10-20 t/year, in a batch operation, since the pressure in the plant will change constantly with increasing fill level. The latter renders continuous operation in the vaporization part of the plant impossible or would necessitate a substantial and complicated technical effort.